1. Field of the Invention
The present invention relates to a multichip sensor configured such that at least an element chip including a detection element of a sensor and a signal-processing IC chip including a signal-processing IC for processing an output signal of the detection element are accommodated within a package.
2. Description of the Related Art
Conventionally, a vehicular motion control apparatus is widely known for performing vehicle stabilization control for maintaining running stability of a vehicle at the time of cornering. Generally, the motion control apparatus includes an integral unit and various sensors, such as a yaw rate sensor, which are connected to the integral unit by use of, for example, harnesses and connectors. The integral unit is configured by integration of a hydraulic unit and an electronic control unit (ECU). The hydraulic unit carries a plurality of hydraulic devices, such as a plurality of solenoid valves and a hydraulic pump, for controlling braking force to be applied to wheels. The ECU controls the plurality of hydraulic devices. The integral unit receives signals from the yaw rate sensor and other sensors by means of so-called controller area network (CAN) communication and performs vehicle stabilization control.
In recent years, technology for accommodating a yaw rate sensor in the ECU of the integral unit (i.e., technology for directly mounting a yaw rate sensor on an ECU board (i.e., circuit board)) has been developed (refer to, for example, Japanese Kohyo (PCT) Patent Publication No. 2004-506572). This technology enables not only elimination of the above-mentioned harnesses and connectors, but also elimination, from the yaw rate sensor, of devices required for the above-mentioned CAN communication, such as a CPU and a CAN driver. Thus, the overall cost of manufacturing the motion control apparatus can be reduced.
A yaw rate sensor to be mounted directly on an ECU board assumes the form of a multichip sensor as described in, for example, Japanese Patent Application Laid-Open (kokai) No. 2001-91613. FIGS. 4A to 4C (plan view, front view, and right side view) show a typical multichip sensor for yaw rate detection which is mounted directly on an ECU board.
As shown in FIGS. 4A to 4C, a multichip sensor 1 for yaw rate detection includes a lead frame 2; an element chip 3 which includes a detection element for detecting a yaw rate of a vehicle; a signal-processing IC chip 4 which includes a signal-processing IC (custom IC, ASIC) for processing an output signal of the detection element; a package 5 which accommodates the lead frame 2, the element chip 3, and the signal-processing IC chip 4; and a plurality of terminals 6 which project from the package 5.
The element chip 3 and the signal-processing IC chip 4 are accommodated in the package 5 in such a manner that planes thereof (along which the element chip 3 and the signal-processing IC chip 4 extend, respectively) and a surface S of the package 5 for mounting on an ECU board (hereinafter may be called the “surface-for-mounting-on-ECU-board”) are in parallel with one another (i.e., in parallel with an X-Y plane).
The yaw-rate detection element of the element chip 3 is a detection element of an ordinary gyro sensor which utilizes a Micro-Electro-Mechanical System (MEMS), whose development has been accelerated in various technical fields in recent years. The detection element of the gyro sensor is configured so as to detect a rotational rate about an axis perpendicular to the plane thereof.
Accordingly, the element chip 3 shown in FIGS. 4A to 4C is configured so as to detect a rotational rate about the Z-axis. In order to detect a yaw rate of a vehicle, the multichip sensor 1 for yaw rate detection shown in FIGS. 4A to 4C must be mounted directly on an ECU board such that the plane of the element chip 3 (surface-for-mounting-on-ECU-board S (X-Y plane)) is horizontal. Thus, the plane of the ECU board in the above-mentioned integral unit must be horizontal.
However, in the above-mentioned integral unit, in many cases, the ECU board is attached to a predetermined vertical surface of a hydraulic unit body in order to fulfill a desire to lay out of a plurality of hydraulic devices within the hydraulic unit. In other words, there arises a problem that the surface-for-mounting-on-ECU-board S of the package 5 must be vertical to the plane of the ECU board.
A conceivable solution of the above problem is that the position and direction of the terminals 6 projecting from the package 5 are changed so as to change the surface-for-mounting-on-ECU-board of the package 5 from the surface S (X-Y plane) to a surface S′ (Y-Z plane shown in FIG. 4B). In other words, the conceivable solution is to lay the plane of the element chip 3 and the plane of the signal-processing IC chip 4 vertical to the surface-for-mounting-on-ECU-board S′. By this procedure, as shown in FIG. 5, when the surface-for-mounting-on-ECU-board S′ of the package 5 (X-Y plane) is mounted directly on a vertical ECU board B, the plane of the element chip 3 (X-Z plane) lies horizontal.
However, in this case, since the signal-processing IC chip 4 also lies horizontal, the multichip sensor 1 for yaw rate detection requires a great height (horizontal length W in FIG. 5) from the ECU board B. This is because the size (length of a side of the top or bottom surface) of the signal-processing IC chip 4 is usually greater than that of the element chip 3.
Thus, in the case where the plane of the element chip is vertical to the plane of the ECU board (i.e., to the surface-for-mounting-on-ECU-board of the package), reducing the height of the multichip sensor from the surface-for-mounting-on-ECU-board has been desired.